Compact fuel injection nozzle

ABSTRACT

A compact fuel injection nozzle includes a unitary nozzle body, a nozzle cap, a valve member and a spring sub assembly. The spring sub assembly provides a biasing force against a valve member that includes an integral lift stop. The biasing force holds the nose of the valve member against the valve seat of the nozzle body until the fuel pressure inside the injector exceeds a minimum opening pressure. The lift stop provides a stop limit, permitting the valve member to move away from the valve seat a predetermined axial distance. The minimum opening pressure and valve opening axial distance may be calibrated by selection and installation of shims.

This application is a National Stage Application under 371 ofPCT/US00/31537 filed Nov. 17, 2000 which claims the benefit of U.S.Provisional Application 60/166,031 filed Nov. 17, 1999.

BACKGROUND OF THE INVENTION

This invention relates generally to a fuel injection nozzle. Moreparticularly, the present invention relates to a fuel injection nozzlefor an internal combustion engine.

Fuel injectors of the type contemplated by the present invention have aplunger or valve which is lifted from its seat by the pressure of fueldelivered to the injector by an associated high pressure pump inmeasured charges in timed relation with the associated engine.Representative fuel injector assemblies are described in U.S. Pat. Nos.3,829,014, 4,205,789, 4,790,055, and 4,938,193.

The improvements in fuel injection nozzles chronicled by the successionof patents identified above, have been performance related and/ormanufacturing related. In the present competitive market for these typesof devices, the need to reduce the cost of materials and fabricationwithout compromising performance continues to be a primary factor.Although some of the devices represented by the prior art provided forimprovements in materials and fabrication, further improvements arerequired.

Many internal combustion engines that utilize fuel injection nozzles arefound in automotive applications. A fuel injection nozzle provides thepath for injecting fuel into the combustion chamber of the internalcombustion engine. Extensive analysis of the combustion process revealsthat the most efficient injection point (in some cases) is at the topand center of the combustion chamber. In overhead cam engines the areaimmediately above the combustion chamber is occupied by the overhead cam(or cams) valve assemblies and connecting mechanisms, such as rockerarms, etc. Placement of injector nozzles in the midst of the valve trainmakes severe constraints on the length, diameter and overall size of theinjector nozzle. Consequently, any reduction in size in the injectornozzle component provides improved flexibility of use.

Additionally, the tip of an injector nozzle includes discharge aperturesfrom which pressurized fuel is delivered into the combustion chamber.Typically, the inside surface of the injector nozzle tip forms a valveseat for sealing with the injector valve between injection pulses. Thisvalve seat/valve interface must form a reliable seal over a useful lifethat will encompass many millions of injection cycles. Materials forinjection valves and injection nozzle tips therefore must be extremelytough, durable, i.e. hard materials. Injector nozzle tips are alsosubjected to high temperatures and pressures present in the combustionchamber. In high output or turbo-charged engines the temperature in thevicinity of the nozzle tip may well exceed 500° F. for sustained periodsof time. Materials used for fuel injection valves and nozzle tips musttherefore meet the dual requirements of maintaining their toughness overmillions of cycles at sustained high temperatures. This has meant theuse of specialty alloy steels having high Rockwell hardness and hightemperature tempering properties.

Materials having these properties are typically both expensive andnotoriously difficult to work with. The result has been that only thecritical portions of the fuel injection nozzle were made from the exoticalloy steels, with the balance of the injector nozzle being moreconventional steel. Assembly of injector nozzles from multiple partsincreases both the cost and complexity of the manufacturing process.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a fuelinjection nozzle assembly in which the component parts are simplyfabricated, easily assembled by automated processes, and readilyinstalled in an engine, without compromising the performance of thenozzles.

Another object of the present invention is to provide a fuel injectionnozzle assembly that has a compact size in relation to conventional fuelinjection nozzle assemblies.

A further object of the present invention is to provide a fuel injectionnozzle assembly in which the entire fuel injection nozzle body,including valve guide and nozzle tip, is made from a single piece ofhomogeneous material.

A yet further object of the invention is to provide a compact fuelinjection nozzle assembly requiring fewer parts.

These objects are accomplished in accordance with the invention throughimprovements in several aspects of the conventional fuel injectionnozzle assembly.

A fuel injection nozzle in accordance with the invention includes aone-piece integral nozzle member. The nozzle member has a lower portionthat is mounted in a socket in the engine cylinder head such that thenozzle tip of the lower portion is positioned within the cylinder head.An upper portion of the nozzle member projects above the cylinder head.The nozzle member also includes an axial bore and a fuel inlet orificeintersecting the axial bore. The inside surface of the axial boreadjacent the nozzle tip defines a valve seat. A fuel inlet member has afuel passage extending from an inlet end portion to an outlet endportion. The outlet end portion is affixed in fluid communication withthe fuel inlet orifice of the nozzle member. The inlet end portion maybe mounted directly to the fuel pump. A cap member has a lower portionmounted to the upper portion of the nozzle member.

A valve member received in the axial bore reciprocates in response toperiodic pulses of pressurized fuel fed to the axial bore via the fuelinlet orifice. The valve is a one-piece member extending from a nose endconfigured to seal against the valve seat to an axially opposed liftstop. The valve member includes an actuating surface, a bearing surfaceand a spring seat.

An upper portion of the cap member and the upper portion of the nozzlemember define a spring chamber. A spring subassembly disposed within thespring chamber includes a spring disposed around the lift stop andseated against the spring seat, a lift shim disposed adjacent the capmember, and an opening pressure shim disposed intermediate the lift shimand the nozzle member. The opening pressure shim has an axial opening.The upper end portion of the lift stop is received within the opening ofthe opening pressure shim. The upper end of the spring engages theopening pressure shim.

The minimum opening pressure and valve lift can be calibrated byinstallation of lift and opening pressure shims of different axialthicknesses. Measurements of injector nozzle components permitcalculation of the correct shim thicknesses.

Other objects and advantages of the invention will become apparent fromthe drawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood and its numerous objectsand advantages will become apparent to those skilled in the art byreference to the accompanying drawings in which:

FIG. 1 is an elevation view, partly in section, of a first prior artfuel injection nozzle;

FIG. 2 is an elevation view, partly in section, of a second prior artfuel injection nozzle;

FIG. 3 is an elevation view, partly in section, of a compact fuelinjection nozzle in accordance with the present invention;

FIG. 4 is an exploded view, partly in section, of the nozzle of FIG. 3,more clearly illustrating the individual components and the manner inwhich the components are assembled;

FIG. 5 is an elevation view, partly in section of a second embodiment ofa compact fuel injection nozzle in accordance with the presentinvention;

FIG. 6 is an elevation view, partly in section of a third embodiment ofa compact fuel injection nozzle in accordance with the presentinvention; and

FIG. 7 is an enlarged elevation view of the compact fuel injectionnozzle illustrated in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a first conventional fuel injection nozzle 10 having anozzle body 12, a nozzle cap 14, a fuel inlet stud 16, and a leak-offcap 18. During operation, fuel is supplied through passages 20 in thefuel inlet stud 16, to a valve chamber 22 in the upper portion of thenozzle body 12. An elongated nozzle valve 24 is axially reciprocablewithin the nozzle body 12 and includes a conical nose 26 at its lowerend for sealing against a valve seat 28 and intermittently providingflow through discharge apertures 30 in the nozzle tip. Fluid at lowpressure exits the nozzle cap 18 through a channel 32 leading tochannels 34 in the hydraulic connections 36 of the leak-off cap 18.

The primary function of the spring chamber 38 in the nozzle cap 14 is toproperly position the spring subassembly 40. The spring subassembly 40in the nozzle cap 14 includes a central lift stop 42, a coil compressionspring 44 and spring seats 46, 48, arranged for biasing the valve 24downwardly to close the valve and establish a minimum opening pressure.The spring seat 46 includes a generally disk-shaped base portion forcontacting the upper end of the valve, and a pedestal portion projectingupwardly therefrom. The lift stop 42 includes a stem portion axiallyaligned with another spring seat 48 and an integral head portion whichis received in abutting relation with the dome of the cap 14. Theradially outer portions of the spring seats 46, 48 are adapted to engagethe ends of the coil spring 44 and to hold it in a compressed(preloaded) condition within the spring chamber 38.

The fabrication of the prior art nozzle 10 begins with the transverseattachment of the inlet stud 16 to the nozzle body 12. The ring portion50 has an inner diameter at ambient temperature that is smaller than theouter diameter of the nozzle body 12 portion to which it will beconnected. The ring portion 50 is first heated to expand the innerdiameter to a dimension greater than the outer diameter of the bodyportion. The ring 50 is then slipped over the body portion apredetermined distance relative to the upper end of the nozzle body 12.The ring 50 is cooled to form a rigid, shrink-fit, annular connectionwith the body portion, in such a manner to prevent leakage pathformation. A drilling tool is then inserted into passage 20 and isadvanced to penetrate the remaining material in the ring portion 50 andthe adjacent wall of the nozzle body 12. The passage through the ringportion 50 into the chamber 22 is reamed, deburred and then burnished.The step of burnishing provides a fluid seal at the juncture of thesecond passage with the interface between the nozzle body exterior andthe ring interior.

The outer, cylindrical mounting portion of the guide member 52 ismachined to provide an appropriate interference fit against the wall ofthe valve chamber 22 upon insertion into the nozzle body 12. Theforward, or downward portion of the guide member 52 includes a recessed,annular space 54 which, after insertion of the guide member 52 into thevalve chamber 22, is in fluid communication with the passage 20 from theinlet stud 16. The two annular edges defining the recess 54 provide an“edge filter” effect such that fuel entering the recess 54 must passover the edges in order to reach the valve chamber 22.

The next steps include: orienting and assembling the nozzle tip 56 intoa press-fit and preferably staked relation with the tip cavity 58;measuring the dimensions of the interior of the guide member 52;selecting a valve 24 having a bearing surface of appropriate dimensionsfor proper diametrical clearance and inserting it into the nozzle bore;and assembling the spring subassembly 40.

Before the spring subassembly 40 is assembled and inserted into thespring chamber 38 of the cap 14, the critical dimensions are checked. Inthe case of a fuel injector, there are two primary critical dimensions.The first critical dimension is the “as assembled” distance between theupper end of the valve 24 and the dome of the cap 14. “As assembled” isthe distance between these two points in an assembled injector. Thisdistance can be determined from automated measurement of the nozzle body12 with valve 24 inserted at one station, and measurement of the cap 14and internal components thereof at another station. When this distanceis known, the correct axial dimension (length) for the lift stop 42 canbe determined. A lift stop 42 having the correct axial length willaccurately permit the valve member to open a predetermined distance. Theconsistent accuracy of the valve opening distance is critical to theproper functioning of the injector.

The second critical dimension is the axial length of the spring 44 whenthe spring is preloaded (partially compressed) to a tension that willhold the valve 24 closed until the desired minimum opening pressure isexerted on the actuating surface 25 of the valve 24. The axial length ofthe preloaded spring is used to determine the correct axial dimension ofthe lift stop head, which in turn determines the axial position of theupper spring seat 48 with respect to the lower spring seat 46.

The head and the nose on the lift stop 42 are ground as necessary foradjusting the critical dimensions. After grinding, the springsubassembly 40 is inserted into the nozzle cap 14, which is then torquedonto the upper end of the nozzle body 12. A plastic or metal leak-offcap 18 is snapped on over the upper end of the nozzle cap 14. Theleak-off cap 18 forms one or more annular recesses with the nozzle cap14, leading to radial flow channels in fluid communication with theleak-off channel in the nozzle cap 14, whereby fluid at low pressurewithin the nozzle cap 14 can be diverted away and recycled if desirable.

In the second prior art fuel injection nozzle 10′ shown in FIG. 2, thecritical dimensions may be threadably adjusted by the pressure screw 60and the lift screw 62. After the critical dimensions are set, thepressure screw 60 and lift screw 62 may be locked in place by a pressurelocknut 64 and a lift locknut 66, respectively.

These prior art assembly configurations and methods of assembly requiremany precision parts and the intervention of skilled personnel in theassembly process. Such skilled personnel add to the cost of producing afuel injection nozzle. In addition, human intervention in the productionprocess may produce variable results depending upon the skill and/orattentiveness of the individual. As can be seen from FIGS. 1 and 2, theprior art injector nozzle bodies 12 and 12′ required the insertion of aseparate nozzle tip 56 and guide member 52. A compact fuel injectionnozzle as described below incorporates the nozzle tip and guide memberinto a unitary injector nozzle body and permits adjustment of criticaldimensions by the selection of appropriately dimensioned shims. Acompact fuel injection nozzle in accordance with the present inventioncan be assembled more efficiently and with less human intervention thanprior art fuel injection nozzles. Ultimately, a compact fuel injectionnozzle may be assembled in a fully automated process.

With reference to FIGS. 3 and 4, wherein like numerals represent likeparts throughout the figures, a compact fuel injection nozzle inaccordance with the present invention is generally designated by thenumeral 68. The compact fuel injection nozzle 68 includes a nozzle body70, a valve member 82, a spring subassembly, a nozzle cap 72, and a fuelinlet 74. Fuel is supplied through a passage 76 in the fuel inlet 74, toa valve chamber 78 in the upper portion 80 of the nozzle body 70. Anelongated nozzle valve 82 axially reciprocates within an axial bore 84in the nozzle body 70 such that a conical nose 86 at its lower end sealsagainst a valve seat 88, intermittently providing flow through dischargeapertures 90 in the nozzle tip 92.

A lower portion 93 of the nozzle body 70 is mounted within a socket inan engine cylinder head (not shown) such that the upper portion 80 ofthe nozzle body 70 projects outwardly from the cylinder head and theintermittent flow of fuel is discharged into the cylinder. Pressurizedfuel is forced (leaks) into the gap 94 between the bearing surface 96 ofthe nozzle valve 82 and the inside surface 98 of the axial bore 84 andprovides lubrication between the nozzle valve 82 and the nozzle body 70.The valve 82 is reciprocated as a result of the intermittent fuel pulsesentering the valve chamber 78, which apply hydraulic pressure on theactuating surface 100 of the valve 82. Hydraulic pressure from fuelpulses lift the valve nose 86 off the valve seat 88, exposing thedischarge apertures 90 to the high pressure fuel occupying the axialbore 84 of the nozzle body 70. Fuel under high pressure is then forcedthrough discharge apertures 90 into the cylinder for combustion.

An upper segment 102 of the upper portion 80 of the nozzle body 70 hasan outside diameter 104 that is less than the outside diameter 106 ofthe lower segment 108 of upper portion 80, forming an upwardly facingshoulder 110. The outside surface of upper segment 102 has a threadsurface 112. The inner surface of the lower portion 114 of the nozzlecap 72 has a thread surface 116 that is complementary with the threadsurface 112 on upper segment 102. When the nozzle cap 72 is installed onthe nozzle body 70, the lip 118 of the nozzle cap 72 engages theshoulder 110 on the nozzle body 70. The threaded engagement between thelower portion 114 of the nozzle cap 72 and the upper segment 102 of thenozzle body 70, together with a compressed annular gasket or O-ring 71provide a substantially leak-tight seal. Preferably, the outsidediameter 120 of the nozzle cap 72 is substantially equal to the outsidediameter 106 of the upper portion 80 of the nozzle body 70 such that theoutside surface of the assembled fuel nozzle 68 has a uniformappearance.

With reference to the embodiment of the compact fuel injection nozzleillustrated in FIGS. 3 and 4, the fuel inlet 74 is a single unitarypipe-like or tube-like structure having an inlet end portion 122removably mounted to a fuel pump (not shown) and an outlet end portion124 which is fixedly mounted to the nozzle body 70. In this embodiment,the outlet end portion 124 of the fuel inlet 74 is disposed within atransverse bore 126 which extends from the outer surface of the nozzlebody 70 to an abutment face 128 positioned such that transverse bore 126intersects valve chamber 78. A fuel passage 76 provides fluidcommunication between the fuel pump and the valve chamber 78. Thetransverse bore 126 may extend through the valve chamber 78 such thatthe abutment face 128 is positioned in the opposite wall, as shown inFIG. 3. Alternatively, the abutment face 128 may be positioned at apoint intermediate the outer edge of the valve chamber 78 and themid-point of the valve chamber 78.

A valve member 82 extends from a nose end 86 to the head 148 of theintegral lift stop 138. A stem 85 connects the nose end 86 to theactuating surface 100, bearing surface 96 and spring seat 156 machinedon the length of the valve member 82. The valve member 82 is received inthe axial bore of the nozzle body 70 with the nose end adjacent thevalve seat 88. The bearing surface 96 is closely received by the valveguide surface 98 so the valve member is supported for axial movement.

The upper segment 102 of the nozzle body 70 forms a cavity 130, which,together with the upper portion 132 of the nozzle cap 72, define aspring chamber 134. A spring subassembly 136 housed in the springchamber 134 includes a coil compression spring 140, a lift shim 142, andan opening pressure shim 144, arranged for biasing the valve 82downwardly to close the valve and establish a minimum opening pressure.The spring 140 surrounds the lift stop 138 with the lower end 154 of thespring 140 bearing against the spring seat 156 of the valve member 82.The disc-shaped lift shim 142 has a top surface 158 that abuts theinside surface 160 of the dome of the cap 72. The washer-shaped openingpressure shim 144 has an axial opening 162 sized to slidably receive thehead end 148 of the lift stop 138. The pressure shim 144 has an uppersurface 164 which abuts the bottom surface 166 of the lift shim 142 anda lower surface 168 which engages the upper end 170 of spring 140.

FIGS. 5 and 6 illustrate alternative preferred embodiments of thecompact fuel injection nozzle 68′ and 68″. With reference to FIG. 5,alternative embodiment 68′ incorporates an alternative configuration forattaching the fuel inlet member 74 to the nozzle body 70. The middlesegment 204 of the nozzle body 70′ has a diameter that is less than theupper portion 80 of the nozzle body, forming a downwardly facingshoulder 208. A banjo-type fitting 200 includes an opening 202 toreceive the middle portion 204 of the nozzle body 70 and an opening 206orthogonal to the nozzle body to receive the outlet end portion 124 ofthe fuel inlet member 74.

The fitting 200 is preferably brazed to the outlet end portion 124 ofthe inlet member 74. The fitting 200 is then mounted to the nozzle body70′ with the fitting abutting the downward facing shoulder 208. Theaxial location of the shoulder 208 and the configuration of the fitting200 serve to axially align the fuel passage 76 of the fuel inlet member74 with the fuel inlet 210 in the injector nozzle 70′. Angular alignmentof the fuel passage 76 and the fuel inlet 210 may be accomplished by anynumber of known methods. The fitting 200 is then preferably brazed tothe nozzle body 70 to form a durable, sealed joint.

FIG. 6 illustrates a further preferred embodiment 68″ in which the outerdiameter of the upper portion 80″ of the nozzle body 70″ is reduced,resulting in a narrowed downward facing shoulder 208′. The fitting 200is assembled to the nozzle body 70″ and the outlet end portion 124 ofthe fuel inlet 74 in the same manner as described with respect toembodiment 68′. Fitting 200 extends radially beyond the narroweddownward facing shoulder 208′, forming an upward facing shoulder 110′.The configuration of the cap 72″ is altered to abut the new, lowerupward facing shoulder 110′ when assembled. This alternative embodiment68″ results in the use of less tool steel to form the nozzle body 72″,further reducing the cost of production.

In all respects other than those described, alternative embodiments 68′and 68″ are configured and function substantially the same as embodiment68.

It will be noted that the cap 72′, 72″ of the compact fuel injectionnozzle 68′, 68″ includes an external annular groove 230. This groove 230is used to facilitate removal of the fuel injection nozzle 68′, 68″ fromthe cylinder head of an engine (not illustrated) as explained in U.S.Pat. No. 4,790,055.

The nozzle body 70 is preferably manufactured from a single, unitarypiece of M50 tool steel that can be heat-treated to a hardness ofRockwell C 60-C 64. The term “unitary” as used in this applicationrefers to a single piece of homogeneous material, in this case M50 alloytool steel. Of course, other alloy steels or materials may beappropriate. When purchased as bar stock, the M50 tool steel is ofmoderate hardness (approximately Rockwell C 20-25) and is readilymachinable using standard machining methods. From bar stock, a nozzlebody 70 is machined to include the required external dimensions, cavity130 and a rough axial bore 84. An appropriate transverse bore 126, orfuel inlet orifice 210 is machined to intersect with axial bore 84.

Assembly of the nozzle 68 begins with the transverse attachment of thefuel inlet 74 to the nozzle body 70. The outlet end portion 124 of thefuel inlet 74 is inserted into the transverse bore 126 until the outletend 172 engages the abutment face 128. The outside surface of the fuelinlet 74 is brazed to the outside surface of the nozzle body 70 tofixedly mount the fuel inlet 74 to the nozzle body 70 and to prove afluid-tight seal between the fuel inlet 74 and the nozzle body 70.

Assembly of alternative embodiments 68′, 68″ begins with attachment ofthe fitting 200 (containing the outlet end portion 124 of the fuel inlet74) to the nozzle body 70′, 70″. Preferably the fitting is brazed inplace to provide a strong, fluid tight bond between the fitting 200 andthe nozzle body 70′, 70″.

For all embodiments 68, 68′, 68″, the brazing process takes place in afurnace where the assembled nozzle body 70, 70′, 70″, fitting 200 (ifappropriate) and fuel inlet 74 are heated to a temperature ofapproximately 2,100° F. Copper material, inserted between the partsduring assembly, melts in the heat and flows to form the brazed joint.The alloy steel of the nozzle body 70, 70′, 70″ is hardened by the cycleof heating and cooling experienced in the furnace. The alloy steel,which was formerly Rockwell C (R_(c)) 20-25, is hardened to a Rockwell C(R_(c)) 60-64. The alloy steel nozzle body is then tempered at atemperature of approximately 1,100° F. to relieve internal stresses inthe crystal structure that occur during the brazing/hardening process,as is known in the art.

The next step is to use an Electrical Discharge Machine to produce thefine discharge apertures 90 in the now hardened and tempered nozzle tip92. Precise grinding tools are then used to hone the valve guide surface98 of the axial bore 84 where the bore will guide the axial movement ofthe nozzle valve 82. The bore 84 in this location must be very preciselyconfigured so the gap 94 between the bearing surface 96 of the valve 82and the valve guide surface 98 meets strict tolerances. The valve seat88 is also ground to a specified configuration. Cutting lubricant may beinjected into the axial bore 84 through the discharge apertures 90 inthe tip as well as from the direction of the honing/lapping tool (notillustrated) to cool and lubricate the honing/lapping tools. Thelubricant is injected at high pressure to ensure adequate cooling andeject any removed material. The shortened length of the axial bore 84 inthe compact fuel injection nozzle decreases the length of the lappingtool used to configure the valve seat 88. A shorter tool has increasedrigidity at its grinding tip, resulting in acceptable accuracy in thevalve seat configuration.

Assembly of the internal parts of the compact fuel injection nozzle inaccordance with the present invention will be described with referenceto the embodiment illustrated in FIGS. 3 and 4. It will be understood bythose of skill in this art that the methods described with reference toembodiment 68 are equally applicable to alternative embodiments 68′ and68″.

Next, a nozzle valve 82 having a bearing surface 96 of appropriatedimensions for proper diametrical clearance (as described above) isinserted into the axial bore 84 and the distance between the head end148 of lift stop 138 and a reference point 174 on the valve body 70 ismeasured. The relative position of the spring seat 156 with respect toreference point 174 is also measured. It will be understood by those ofordinary skill in the art that reference point 174 is arbitrary. Allthat is important about the reference point is that the same point beused consistently.

A lift shim 142 having a thickness determined by the measured distancebetween head end 148 and reference point 174 is selected from a familyof lift shims 143. The family of lift shims 143 comprises a number oflift shims having different predetermined thicknesses. The number oflift shims and the thickness of each lift shim in the family 143 areselected such that the selected lift shim 142 substantially corrects theaccumulated tolerances for the spring subassembly components withoutrequiring the machining of any such components. Selecting an appropriatelift shim 142 from a family of lift shims 143 thereby eliminates one ormore machining steps that were required to manufacture the first priorart nozzle 10. In addition, selecting an appropriate lift shim 142 froma family of lift shims 143 thereby eliminates the lift locknut 66 andpressure locknut 64 required to manufacture the second prior art nozzle10′.

The relationships between the parts contained in the spring chamber 134are best illustrated with reference to FIG. 7. A compact fuel injectionnozzle 68′ is configured so that the valve member 82 moves axially awayfrom the valve seat 88 by a predetermined valve lift distance inresponse to a predetermined fuel pressure (minimum opening pressure) inthe axial bore 84. The opening distance and the minimum opening pressureare determined by the components in the spring chamber 134 acting on thevalve member 82.

An assembled cap 72′ and nozzle body 70′ have a fixed relationship toone another, resulting in a fixed distance from the valve seat 88 to theinside surface 160 of the cap 72″. To establish the opening distance ofthe valve member 82, the position of the head end 148 of a seated valvemember 82 is measured with respect to some part of the nozzle body 70′.The “as assembled” relationship of the inside surface 160 of the cap 72′relative to the part of the nozzle body are known and permit thecalculation of the distance between the head end 148 of the valve member82 and the inside surface 160 of the cap (shown in FIG. 7 as B).Distance B minus the axial thickness of lift shim 142 equals the valvelift distance. The valve lift distance may be adjusted by selection oflift shims from a family of lift shims having various axial thicknesses.

When the appropriate lift shim 142 has been selected, distance E betweenthe bottom surface 166 of the lift shim 142 and the spring seat 156 ofthe valve member 82 can be calculated. The axial length of a correctlypreloaded spring is preferably determined by bench testing. Knowing theaxial length of the preloaded spring 140 and distance E, the axialthickness D of opening pressure shim 144 can be determined and theappropriate opening pressure shim selected from a family of openingpressure shims 145 having various axial thicknesses.

Thus, by simple and reliable bench measurements, it is possible to matcha lift shim 142 and opening pressure shim 144 to a given nozzle body70′, valve member 82, cap 72′ and spring 140. A matched set of partswill accurately produce the desired opening distance and openingpressure in the assembled compact fuel injection nozzle 68′. Thismanufacturing process requires no grinding or intervention by highlyskilled personnel to achieve consistently acceptable quality.

It should be appreciated that a compact fuel injection nozzle 68, 68′,68″ in accordance with the invention replaces the nozzle body 12, 12′,nozzle tip 56, 56′ and guide member 52, 52′ of the prior art nozzles 10,10′ with a single, unitary nozzle body 70, 70′, 70″. This eliminates themanufacturing steps required to manufacture each of the three componentsseparately, measuring the guide member 52, 52′ and nozzle tip 56, 56′for fit with the nozzle body 12, 12′, and press-fitting and staking theguide member 52, 52′ and nozzle tip 56, 56′ to the nozzle body 12, 12′.The use of three separate components to form a complete prior art nozzlebody was necessitated by limitations within the prior art manufacturingprocess.

The nozzle tip 56, 56′ and guide member 52, 52′ must be composed of arelatively hard metal to provide the proper operating characteristics.The prior art machining process could not machine the axial bore if thevalve body 12, 12′ was composed of the same material as the nozzle tip56, 56′ and guide member 52, 52′. Consequently, the nozzle body 12, 12′of prior art nozzles 10, 10′ is composed of carbon steel. Themanufacturing process which has been developed to produce the compactfuel injection nozzle 68 utilizes coolant at a higher pressure (up to2000 psi) in a manner which had not been envisioned before. The subjectmanufacturing equipment and process directs a stream of this highpressure coolant into the nozzle body 70 as the axial bore 84 ismachined to cool the work area, provide lubrication, and to eject chipsout of the work area. As a consequence, an accurate axial bore 84 andvalve seat 88 can be ground in the hard material, allowing the entirenozzle body 70 to be manufactured from the same material as a unitarymember. In addition, the manufacturing process can manufacture thecomponents to tighter tolerances.

The overall length of the compact injection nozzle 68, 68′, 68″ is only3.00 inches as compared to an overall length of 4.00 inches for theprior art nozzles. The tip shank minimum diameter of the compactinjection nozzle is slightly greater (0.220 inches) than that of theprior art nozzles (0.214 inches) and the injector minimum shank diameteris substantially the same as that of the prior art nozzles (0.374inches). It should be appreciated that the reduced length of the compactnozzle provides increased flexibility of use. It should also beappreciated that the small difference in the tip shank minimum diameterhas substantially no impact on the use of the compact injection nozzle68.

Prior art nozzles 10, 10′ require a leak-off path to allow the nozzlesto be properly tuned in a cost-effective manner. The use of tightertolerances in conjunction with a fuel injection pump assembly thatpermits pressures in the fuel inlet 74 to bleed down between injectioncycles has eliminated the need to provide a fuel leak-off path.Consequently, the leak-off cap 18, 18′ of the prior art nozzles 10, 10′has been eliminated. This feature is particularly advantageous when theinjector nozzle is located in the midst of the valve train, becauseseveral possible sources of fuel leaks are eliminated.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration and not limitation.

1. A fuel injection nozzle assembly for providing fluid communicationbetween a fuel pump and an engine including a cylinder and a cylinderhead having a socket, the nozzle assembly comprising: a unitary nozzlemember having a lower portion for mounting in the socket and an upperportion for projecting above the cylinder head, the lower portionterminating in a nozzle tip for insertion into the cylinder, the nozzlemember defining an axial bore and a fuel inlet orifice intersecting theaxial bore, an inside surface of said axial bore adjacent said nozzletip defining a valve seat; a fuel inlet member defining a fuel passageand having oppositely disposed inlet and outlet end portions, the outletend portion being affixed in fluid communication with said fuel inletorifice, the inlet end portion being mountable to the fuel pump; a capmember having upper and lower portions, the lower portion of the capmember being mounted to the upper portion of the nozzle member, theupper portion of the cap member and the upper portion of the nozzlemember defining a spring chamber; a unitary valve member disposed toaxially reciprocate within the axial bore of the nozzle member, thevalve member having oppositely disposed nose end and head ends, the noseend being disposed adjacent said nozzle tip, and including an integralspring seat and axially extending lift stop terminating at said headend; and a spring subassembly disposed within the spring chamber, thespring subassembly including a spring disposed around the lift stop, atleast one lift shim having an axial thickness (B) disposed adjacent thecap member, and an opening pressure shim disposed intermediate the liftshim and the nozzle member, the opening pressure shim defining an axialopening, the head end of the lift stop being received within an axialopening of the opening pressure shim, the spring being compressivelyengaged between the opening pressure shim and the spring seat, whereinsaid valve member reciprocates a first axial distance between a closedposition in which said nose end is in close contact with said valve seatand an open position in which said head end is in contact with said liftshim, said first axial distance being adjustable by selection andmounting of said at least one lift shim from a family of lift shimshaving axial thicknesses (B), said valve member moving axially away fromsaid valve seat in response to a minimum opening pressure exerted on anactuating surface of said valve member by a charge of pressurized fuelin said axial bore and said minimum opening pressure is adjustable byselection and mounting of at least one opening pressure shim having anaxial thickness (D) from a family of opening pressure shims, the axialthickness (D) of said at least one opening pressure shim being at leastpartially dependent upon the axial thickness (B) of the at least onelift shim.
 2. The fuel injection nozzle of claim 1, wherein said familyof lift shims comprises at least two lift shims having different axialthicknesses (B).
 3. The fuel injection nozzle assembly of claim 1,wherein said family of opening pressure shims comprises at least twoopening pressure shims having different axial thicknesses (D).
 4. Thefuel injection nozzle assembly of claim 1, wherein said nozzle bodyconsists essentially of alloy tool steel.
 5. A method for manufacturinga compact fuel injection nozzle assembly having an elongated, generallycylindrical spring chamber at one end and an axial bore extending fromthe spring chamber to a nozzle tip including an inside surface defininga valve seat, said manufacturing method comprising the steps of:mounting a fuel inlet member to a nozzle member with a fuel passagedefined by said nozzle member in fluid communication with a fuel inletorifice in said nozzle member; inserting a valve member having anintegral lift stop axially extending from a spring seat to a head endinto the axial passage until the nose end contacts the valve seat andthe head end is disposed in the spring chamber upper portion; selectinga nozzle cap comprising means for rigidly securing the nozzle cap to thenozzle member and defining an upper inside surface, wherein the distancebetween the upper inside surface of a rigidly mounted nozzle cap and areference point on said nozzle member is known; measuring the positionof the head end relative to the reference point on said nozzle member;measuring the position of the spring seat relative to the referencepoint on said nozzle member; calculating the positions of said head endand spring seat relative to the inside surface of a rigidly mountednozzle cap; measuring the compressed length of a spring for providing adesired downward biasing force against the valve; calculating an axialthickness of a lift shim where the lift shim axial thickness (B) equalsthe distance between the head end and the cap member upper insidesurface minus a desired axial gap; selecting a lift shim having saidcalculated axial thickness (B); installing said lift shim within saidcap member so that said lift shim abuts said cap member upper insidesurface; calculating an axial thickness of an opening pressure shimwhere the opening pressure shim axial thickness (D) equals the distancebetween the spring seat and the cap member upper inside surface minusthe sum of the compressed length of the spring and the axial thickness(B) of the lift shim; selecting an opening pressure shim having saidcalculated axial thickness (D); installing said opening pressure shim insaid cap member so that said opening pressure shim abuts said lift shim;installing the spring over said lift stop; and rigidly securing said capmember to said nozzle member with said spring engaged between saidopening pressure shim and said spring seat, wherein said axial thickness(B) of said lift shim and said axial thickness (D) of said openingpressure shim affect an opening pressure at which said valve membermoves away from said valve seat in response to pressurized fluid in saidaxial passage.
 6. The manufacturing method of claim 5, wherein saidaxial gap is inversely proportional to the lift shim axial thickness(B).
 7. The manufacturing method of claim 5, wherein said desireddownward bias is directly proportional to the sum of said lift shimaxial and opening pressure shim axial thicknesses (B, D).